Theory works great in the classroom, but in practice, knowing the laws governing the topic work much better. The levitical least demonstrate when killing is justified and those same laws are in use today, just different technology and circumstance.
(Exodus 15:3) The LORD is a warrior; Yahweh is His name!
If you have no capacity for violence then you are a healthy productive citizen, a sheep. If you have a capacity for violence and no empathy for your fellow citizens, then you have defined an aggressive sociopath, a wolf. But what if you have a capacity for violence, and a deep love for your fellow citizens? What do you have then? A sheepdog, a warrior, someone who is walking the hero’s path. Someone who can walk into the heart of darkness, into the universal human phobia, and walk out unscathed.
http://treehouseletter.com/2015/01/30/the-sheep-the-wolf-the-sheepdog-ltc-dave-grossman-american-sniper/